The Ethical Challenges of Human-Animal Chimeras, Embryo Models, and In Vitro Brains

Monday - January 8 2024, 12:36 UTC - 10 months ago

In September, scientists at the Guangzhou Institutes of Biomedicine and Health announced they had successfully grown "humanized" kidneys inside pig embryos. The breakthrough suggests it may soon be possible to generate human organs inside part-human "chimeric" animals, but it also raises ethically fraught questions that require a new ethical framework. This requires us to go beyond simplistic categories and ask tough questions about what makes something "naturally" human, and when ethical considerations should come into play.

In September, scientists at the Guangzhou Institutes of Biomedicine and Health announced they had successfully grown "humanized" kidneys inside pig embryos. The scientists genetically altered the embryos to remove their ability to grow a kidney, then injected them with human stem cells. The embryos were then implanted into a sow and allowed to develop for up to 28 days. The resulting embryos were made up mostly of pig cells (although some human cells were found throughout their bodies, including in the brain). However, the embryonic kidneys were largely human.

This breakthrough suggests it may soon be possible to generate human organs inside part-human "chimeric" animals. Such animals could be used for medical research or to grow organs for transplant, which could save many human lives. But the research is ethically fraught. We might want to do things to these creatures we would never do to a human, like kill them for body parts. The problem is, these chimeric pigs aren’t just pigs—they are also partly human.

If a human–pig chimera were brought to term, should we treat it like a pig, like a human, or like something else altogether? Maybe this question seems too easy. But what about the idea of creating monkeys with humanized brains? .

Chimeras Are Only One Challenge Among Many .

Other areas of stem cell science raise similarly difficult questions. In June, scientists created "synthetic embryos"—lab-grown embryo models that closely resemble normal human embryos. Despite the similarities, they fell outside the scope of legal definitions of a human embryo in the United Kingdom (where the study took place). Like human–pig chimeras, synthetic embryos straddle two distinct categories: in this case, stem cell model and human embryo. It is not obvious how they should be treated.

In the past decade, we have also seen the development of increasingly sophisticated human cerebral organoids (or "lab-grown mini-brains"). Unlike synthetic embryos, cerebral organoids don’t mimic the development of a whole person. But they do mimic the development of the part that stores our memories, thinks our thoughts, and makes conscious experience possible. Most scientists think current "mini-brains" are not conscious, but the field is developing rapidly. It is not far-fetched to think a cerebral organoid will one day "wake up." .

Complicating the picture even further are entities that combine human neurons with technology—like DishBrain, a biological computer chip made by Cortical Labs in Melbourne. How should we treat these in vitro brains? Like any other human tissue culture, or like a human person? Or perhaps something in between, like a research animal? .

A New Moral Framework .

It might be tempting to think we should settle these questions by slotting these entities into one category or another: human or animal, embryo or model, human person or mere human tissue. This approach would be a mistake. The confusion sparked by chimeras, embryo models, and in vitro brains shows these underlying categories no longer make sense. We are creating entities that are neither one thing nor the other. We cannot solve the problem by pretending otherwise.

Instead, we must develop a new ethical framework to guide our decision-making. This requires us to go beyond simplistic categories and ask tough questions about what makes something "naturally" human, and when ethical considerations should come into play. We must also grapple with the possibility of creating something that, despite being mostly animal, has a portion of human intelligence. This is not a question of science, but of ethics.

We are on the cusp of a new era of human-animal creations, and the ethical implications are immense. Humans have always tweaked and nurtured natural organisms to create animals, like dogs, that serve us in various ways. But now our capabilities have far exceeded nature. It is time for us to step up and face the reality of the present—not hide behind outdated categories and pretend everything is in its right place.